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Jul 27, 2021
14 min read

7 best diets for weight loss: what works?

Several popular diets include intermittent fasting, Meditteranean diet, DASH diet, keto diet, paleo diet, plant-based eating, and WW. There is no single best diet for weight loss—any diet that uses calorie restriction can help you lose weight. When choosing a diet plan, opt for one that promotes healthy eating and exercise and encourages frequent self-monitoring, like food tracking and weigh-ins. Aim to lose 1–2lbs per week. Avoid diets that claim weight loss without exercise, rapid and significant weight loss in a short amount of time, or diets that force you to eliminate an entire food group.

mike bohl

Reviewed by Mike Bohl, MD, MPH

Written by Chimene Richa, MD


If you have any medical questions or concerns, please talk to your healthcare provider. The articles on Health Guide are underpinned by peer-reviewed research and information drawn from medical societies and governmental agencies. However, they are not a substitute for professional medical advice, diagnosis, or treatment.

If you try to search the internet for the “best diet for weight loss,” you will find a host of sites claiming they have the one-and-only answer to help you lose weight. But is there really one diet that’s the best? How do you know which one is right for you? Read on to find out. 

The science behind weight loss

Studies have shown that the most effective weight loss strategy is calorie restriction—in other words, eating fewer calories (Rynders, 2019). 

You can accomplish this using various diets, like intermittent fasting, the Mediterranean diet, low-fat diets, low-carb diets, etc. Still, the common denominator in a successful diet is taking in fewer calories. Just as people respond differently to medications, you may react differently to various diet plans. A diet that helps your friend reduce their caloric intake may not work for you. 

Find the method that helps you eat fewer calories in the long run, not just for the short term. Keeping the weight off is much more challenging than losing the weight initially. People who successfully attain a healthy weight have incorporated lifestyle changes and healthy food choices into their daily routines.

Many studies have looked at the different diet plans out there, sometimes with conflicting results. The short answer to the science behind dieting is that there is no magic solution or one “perfect diet.” Let’s look at some of the research behind popular diet plans.

1. Intermittent Fasting

Intermittent fasting is what it sounds like—you alternate between eating and fasting on a daily or weekly schedule. There are many different intermittent fasting protocols, but the three most popular ones are alternate day fasting (ADF), time-restricted feeding (TRF), and the 5:2 method. 

With ADF, you eat normally one day, fast the next, and keep alternating in this pattern. Fasting can mean a complete fast, where you consume no calories at all, or a period of significantly reduced caloric intake (usually about 25% of your usual calorie intake or ~500 calories) (Trepanowski, 2017). 

TRF means that you take in all of your calories during a specific “feeding window” and don’t eat anything outside that window. The most common way to do TRF is to restrict the eating window to eight hours. Most people accomplish this by eating their first meal at noon and finishing their last meal at 8 pm; this is commonly referred to as 16:8 (16 hours of fasting followed by eating all meals within an 8-hour window). 

Finally, the 5:2 method consists of eating regularly for five days and fasting for two days per week. The fasting days do not need to be consecutive and, as with ADF, may mean eating nothing at all or just eating very few calories.

How does it work?

Intermittent fasting uses the periods when you don’t eat to decrease your overall daily or weekly calorie intake. In other words, since you are eating for shorter periods, you are taking in fewer calories without actually counting calories. There is no specific restriction on what you eat, just when you eat. 


Current research shows that intermittent fasting works for weight loss because it helps you decrease how much you eat each day. Intermittent fasting is a popular weight loss option because it does not require you to count calories or follow a complicated diet. This makes it easier to stay on the program over longer periods (Lowe, 2020). 


Intermittent fasting does not seem to be any better than overall calorie restriction (Trepanowski, 2017). A recent study also showed that intermittent fasting is not any better than other calorie restricting diets at helping you lose weight (Lowe, 2020).

People with diabetes or taking antidiabetic medications may be at higher risk of developing hypoglycemia (dangerously low blood sugar levels). Healthcare providers may recommend adjusting medications or consulting a specialist (Grajower, 2019).

What to avoid?

When engaging in IF, it is easy to binge during the times you are allowed to eat—this obviously defeats the purpose of following this eating plan. During your eating periods, choose healthy food options like whole grains, lean proteins, and high-fiber fruits and vegetables. Also, make sure to drink plenty of water throughout the day.

2. Mediterranean diet

The Mediterranean diet refers to an overall diet pattern followed by many countries around the Mediterranean sea. It encourages eating a significant amount of healthy foods like fruits, vegetables, nuts, legumes, whole grains, and monounsaturated fats like olive oil, with moderate lean meats (seafood, poultry) and dairy products (cheese, milk, eggs). Generally, eating red meat is limited.  

How does it work?

By emphasizing fruits, veggies, whole grains, and healthy fats like olive oil, the Meditteranean diet guides you to foods that will keep you fuller for longer—this can result in an overall decrease in your caloric intake. 


Olive oil, one of the primary fats in the Meditteranean diet, has antioxidants and essential fatty acids. Studies suggest that this diet may improve your cardiovascular or heart health. Other benefits may include improving cholesterol, decreasing high blood pressure, and lowering blood sugar levels. It may also play a protective role in cancer prevention (Mazzocchi, 2019).


Overall, the Mediterranean diet can help you lose weight. Still, it’s not necessarily better than other diets when used by people who are overweight, have obesity, or are trying to lose weight (Mancini, 2016). 

It may be difficult for some people to adhere to the Mediterranean diet plan exclusively. The diet works best if you use it regularly and consistently. You also need to regulate how much you eat—too many nuts or olive oil can still lead to weight gain. If you have low iron or low calcium, you may need to eat more iron-rich foods or dairy products than is typically recommended on the Mediterranean diet (MedlinePlus, 2020). 

Lastly, some versions of the Mediterranean diet recommend a glass of red wine daily. It may not be appropriate for certain people to follow this guideline, like those who are pregnant or who have liver disease (Rishor-Olney, 2021)

What to avoid

Like any diet, moderation is key for the Mediterranean diet to be effective. The bulk of your foods should be vegetables, fruits, and whole grains. Fats, especially olive oil, are a significant part of the diet—but take care not to overdo how much fats, nuts, or red wine you consume. Too much will defeat the goal of lowering your calorie intake. 

3. DASH diet

Dietary Approaches to Stop Hypertension, or DASH diet, is a diet initially designed to help people lower their high blood pressure (hypertension). The DASH diet emphasizes eating fruits, vegetables, beans, whole grains, low-fat dairy products, and lean proteins, like chicken and fish. It also limits red meat, refined sugars, saturated fat, and sodium (no more than one teaspoon, or 2300 mg, of sodium per day).

How does it work?

The DASH diet limits your sodium intake, which helps lower your blood pressure. When you take in sodium, your body holds on to water to balance things out. The more water you hold onto, the higher your blood pressure (Filippou, 2020). 

This diet also encourages you to eat whole grains, lean proteins, and lots of vegetables and fruits. These foods can help you feel fuller and eat less over the course of the day. 


Numerous studies show that not only does the DASH diet help lower blood pressure, but it can also help lower blood sugar, triglycerides, and cholesterol levels. It may reduce your risk of developing colon cancer and help with other medical conditions like liver disease, heart failure, and celiac disease (Challa, 2021). 

The PREMIER clinical trial looked at over 800 adults and found that not only did the DASH diet improve blood pressure, but when combined with exercise, it also promoted weight loss (Appel, 2003). 


One of the basic tenets of the DASH diet is limiting your sodium intake. According to the FDA, more than 70% of your daily sodium intake comes from processed and prepackaged foods, not your salt shaker. Salt makes foods taste better, and some people who start a low sodium diet find that their food tastes blander. This may be one of the reasons why it can be tough to stay on the DASH diet (FDA, 2021). 

Another disadvantage is that there are not many “convenience” food options for the DASH diet, since we just mentioned that prepackaged foods tend to have more sodium. The effort required to prepare appropriate foods for this diet can be a barrier for many people.  

While DASH is an overall healthy diet plan, people with certain medical conditions like uncontrolled diabetes, kidney disease, heart failure, etc., may need to modify their DASH diet plan (Tyson, 2012). 

What to avoid

The main thing to avoid in the DASH diet is excess salt, specifically sodium—this involves more than just taking it easy with the salt shaker. Most of the sodium you eat comes from prepackaged food, as previously mentioned. But don’t forget about dining out. Around 30% of the average American’s sodium intake comes from eating at restaurants and fast-food chains. You will have to avoid or limit dining out on the DASH diet (Byrd, 2018). 

4. Ketogenic diet

Ketogenic or “keto” diets encourage you to limit your carbohydrate intake to between 20–50 grams per day and eat more fats and proteins. This very low-carbohydrate and high-fat ketogenic diet is very effective for weight loss—at least in the short term (Masood, 2020).

How does it work?

The theory behind the keto diet is that by decreasing how much carbohydrates you eat, you force your body into a state of nutritional ketosis where your liver converts fats into ketones, which can then be used as an energy source in place of carbohydrates. When you are in this ketosis state, your body switches to fat-burning mode (Masood, 2020).  

Some people on a ketogenic diet may feel less hungry and decrease their overall calorie intake, promoting further weight loss without counting calories (Abassi, 2018). 


Many people who start a very low carbohydrate ketogenic diet will notice rapid weight loss in the first two weeks—up to 10 lbs in two weeks or less. This is likely due to a diuretic effect where much of that initial weight loss is water weight, followed by fat loss (Masood. 2020). 


One disadvantage of ketogenic diets is that many people find it tough to stay on this restrictive diet—long-term weight loss may be difficult to achieve (Masood, 2020).

The first few weeks of the diet are often accompanied by the “keto flu,” which includes symptoms of fatigue, irritability, dizziness, bad breath, nausea, vomiting, headache, diarrhea, and constipation. This diet can also lead to long-term side effects like fatty liver disease, low blood protein levels, kidney stones, and vitamin and mineral deficiencies. (Masood, 2020).

If you have diabetes, you may need to have your healthcare provider adjust your medications to prevent dangerously low blood sugars while on this diet. Lastly, people with pancreatitis, liver failure, problems metabolizing fat, or certain enzyme deficiencies should not follow the keto diet (Masood, 2020). 

What to avoid

Avoid dehydration and make sure that you are drinking plenty of fluids on the ketogenic diet—this will help with some of the keto flu symptoms. Don’t follow this diet for more than 6–12 months, and then engage in a gradual transition back to a standard diet.

Since the keto diet is a very low-carbohydrate plan, avoid foods like grains, starchy vegetables, high carbohydrate fruits, sugary foods, soft drinks, etc.

5. Paleolithic diet

The paleolithic diet, also known as the hunter-gatherer or stone-age diet, attempts to recreate the diet that our “caveman” ancestors would have consumed, including (Challa, 2020):

  • Plants like tubers, seeds, nuts, wild-grown barley that was pounded into flour, and legumes
  • Meat like fish, shellfish, lean beef, pork, and poultry, along with game animals
  • Eggs
  • Fruits like berries, citrus fruits, and melons
  • Non-starchy vegetables like greens, peppers, onions, etc.
  • Healthy fats like nuts, seeds, and olive oil

Refined fats and sugars, as well as processed foods, are not allowed. 

How does it work?

The paleo diet’s high protein and low carbohydrate focus are likely the main reasons it works. Both the high protein and high-fiber nature of the foods allowed help you stay fuller longer, eat less overall, and lose weight. 


Several studies show short-term weight loss on the paleo diet (Freire, 2020). 

Some data also suggest that following the paleo diet can decrease your blood pressure, fasting blood glucose (a marker for diabetes), and cholesterol levels in the short term (Manheimer, 2015). 

However, there is conflicting research on whether these effects are any better than other diets, and very few look at the long-term health benefits of the paleo diet plan (Jamka, 2020). 


Like the keto diet, paleo diets are tough to maintain long-term because they are so restrictive. It can also get expensive trying to buy all organic and avoiding any processed foods. Another downside of this diet is that the paleo diet has a potential risk for vitamin D, calcium, and iodine deficiencies (Freire, 2020). 

What to avoid

When thinking about the paleo diet, you need to remember that it is trying to mimic the types of foods that would have been available to our hunter-gatherer ancestors before the onset of animal domestication. Therefore, you should avoid cultivated products, like dairy products, most oils, and many kinds of cereal, as well as salt and refined sugars. The paleo diet also recommends organic, grass-fed meats and avoiding processed foods (Challa, 2020).

6. Plant-based diet

Plant-based diets encourage you to eat more fruits, vegetables, beans, whole grains, nuts, and vegetable oils, while limiting animal products like meat, dairy, and fish. They can vary greatly; some only exclude meat (vegetarian) while others may exclude all animal products (vegan), and still others are somewhere in between. 

How does it work?

Like many other diets on this list, plant-based diets work mainly by encouraging you to eat high-fiber foods like fruits, vegetables, and whole grains. These types of foods are not digested as quickly as sugary foods, so you feel full longer. Feeling full helps you eat less and lose weight. Of course, this won’t work if your plant-based diet consists solely of potato chips and milkshakes—you still need to make healthy food choices (Magkos, 2020)


Some studies show that a plant-based meal plan can help you lose weight; however, other studies indicate that this weight loss is not significant compared to non-vegetarian diets (Freire, 2020). 

Other data suggest that plant-based diets may lower your risk of heart disease and type 2 diabetes (Magkos, 2020).


It is important to note that cutting out all animal products can lead to deficiencies of protein, iron, zinc, calcium, and vitamins D and B12 (Freire, 2020). If you plan to switch to a plant-based diet, consult with your healthcare provider to make sure you are still getting all the necessary nutrients.

What to avoid

The foods you avoid will depend on the type of plant-based diet plan you choose. Flexitarian plans allow for meat in limited amounts, while pescatarian programs allow for fish and seafood. Following a vegan diet is even more strict, with no animal products allowed, including eggs and dairy products. 

7. WW

WW, formerly known as Weight Watchers, is a popular weight loss program that incorporates food tracking, counseling, and limiting the amount of food you eat each day. 

How does it work?

WW focuses on modifying behaviors and diet while increasing physical activity—all to help you lose weight. For their in-person program, you attend weekly meetings led by a WW Lifetime member who has successfully completed the program and received training from the company (Pinto, 2013). You can also track your food and activity using their app.

WW helps you control your calorie intake by assigning point values to different foods and giving you a personalized “allowance” of points per day. You are free to use up those points any way you want, but the idea is not to go “over-budget.” There is also a support community available through the WW app, group sites, etc. 


In a literature review of commercial diet plans, WW participants consistently lost more weight (2.6% more weight loss) after one year than people who only received education about weight loss (Gudzune, 2015).

WW focuses not only on foods but also on behavioral changes, like increasing physical activity, which can help you keep the weight off. Also, by attending the meetings, you have the chance to talk to other people who are potentially struggling with similar issues and may provide you with unique solutions to your weight loss hurdles.


WW comes with the additional cost of paying for the program, starting at around $20 per month. 

What to avoid

Overall, the goal of WW is to help you create a habit of healthy eating. With that said, there are no specific foods you need to avoid. Each food has a point value—more nutritious foods “cost” fewer points than unhealthy foods, like pizza or French fries. If you consume unhealthy foods, you will be limited on how much you can eat for the rest of the day (i.e., you’ll have spent your food point allowance).

What to consider when choosing a diet plan

Despite all of the research available, there is no optimal diet that works for everyone to lose weight. Dieting consists of two phases: losing weight and keeping it off long-term. Highly restrictive diets may jump-start your weight loss, but they do not usually work to keep the weight off long-term because it’s too challenging to stay on a restrictive diet for a long time. 

Avoid yo-yo dieting and look for a diet that encourages healthy lifestyle changes, like whole foods and increased physical activity, to help you be healthy and keep the weight off. Slow and steady weight loss, about 1–2 lbs per week, is best. 

Experts recommend that people who are overweight or have obesity start with a weight loss goal of 5–10% of their starting weight over six months; this translates to a 10–20lb weight loss over six months for someone who weighs 200 lbs at the start of the diet (NIDDK, 2017).  

Ongoing feedback, self check-ins, etc., can go a long way to motivating you to stay on track. Support through friends, family, or the online community can also help you maintain your weight loss. Lastly, remember that several variables can affect how you lose weight, including age, gender, overall health, medications, etc. 

Losing weight can seem like a daunting task, and it is easy to become discouraged and want to quit; knowing that you are not alone can help you get through the tough times. Your goal should not simply be to “lose weight,” but rather, to reach a healthy weight. A healthy weight decreases your risk of heart disease, type 2 diabetes, and high blood pressure, and will help you feel better overall. Work with your healthcare provider to find a weight management strategy that works for you. 

When looking for a safe and successful dieting plan, look for the following:

  • A plan should promote changes that are sustainable in the long term.
  • Avoid diets that eliminate entire food groups or are too restrictive, claim significant weight loss in a very short amount of time, or tell you that you can avoid exercising.
  • For a diet to work, you need to decrease your calorie intake.
  • Have a way to monitor and self-check, like weekly weigh-ins, food tracking, etc.
  • Aim for diets that emphasize whole foods like fruits, vegetables, whole grains, and lean protein.


  1. Abbasi, J. (2018). Interest in the ketogenic diet grows for weight loss and type 2 diabetes. JAMA, 319(3), 215. doi: 10.1001/jama.2017.20639. Retrieved from
  2. Appel, L. J., Champagne, C. M., Harsha, D. W., Cooper, L. S., Obarzanek, E., et al. (2003). Effects of comprehensive lifestyle modification on blood pressure control: main results of the PREMIER clinical trial. JAMA, 289(16), 2083–2093. doi: 10.1001/jama.289.16.2083. Retrieved from
  3. Byrd, K., Almanza, B., Ghiselli, R. F., Behnke, C., & Eicher-Miller, H. A. (2018). Reported action to decrease sodium intake is associated with dining out frequency and use of menu nutrition information among US adults. Journal of the Academy of Nutrition and Dietetics, 118(5), 824–835. doi: 10.1016/j.jand.2017.06.012. Retrieved from
  4. Challa HJ, Bandlamudi M, Uppaluri KR. (2020). Paleolithic diet. In: StatPearls [Internet]. Retrieved from
  5. Challa HJ, Ameer MA, Uppaluri KR. (2021). DASH diet to stop hypertension. In: StatPearls [Internet]. Retrieved from
  6. Filippou, C. D., Tsioufis, C. P., Thomopoulos, C. G., Mihas, C. C., Dimitriadis, K. S., Sotiropoulou, L. I., et al. (2020). Dietary approaches to stop hypertension (DASH) diet and blood pressure reduction in adults with and without hypertension: a systematic review and meta-analysis of randomized controlled trials. Advances in Nutrition (Bethesda, Md.), 11(5), 1150–1160. doi: 10.1093/advances/nmaa041. Retrieved from
  7. Freire, R. (2020). Scientific evidence of diets for weight loss: different macronutrient composition, intermittent fasting, and popular diets. Nutrition, 69, 110549. doi: 10.1016/j.nut.2019.07.001.
  8. Gardner, C. D., Trepanowski, J. F., Gobbo, L. C. D., Hauser, M. E., Rigdon, J., Ioannidis, J. P. A., et al. (2018). Effect of low-fat vs low-carbohydrate diet on 12-month weight loss in overweight adults and the association with genotype pattern or insulin secretion. JAMA, 319(7), 667–669. doi: 10.1001/jama.2018.0245. Retrieved from
  9. Grajower, M. M., & Horne, B. D. (2019). Clinical management of intermittent fasting in patients with diabetes mellitus. Nutrients, 11(4), 873. doi: 10.3390/nu11040873. Retrieved from
  10. Gudzune, K. A., Doshi, R. S., Mehta, A. K., Chaudhry, Z. W., Jacobs, D. K., Vakil, R. M., et al. (2015). Efficacy of commercial weight-loss programs. Annals of Internal Medicine, 162(7), 501. doi: 10.7326/m14-2238. Retrieved from
  11. Jamka, M., Kulczyński, B., Juruć, A., Gramza-Michałowska, A., Stokes, C. S., & Walkowiak, J. (2020). The effect of the paleolithic diet vs. healthy diets on glucose and insulin homeostasis: a systematic review and meta-analysis of randomized controlled trials. Journal of Clinical Medicine, 9(2), 296. doi: 10.3390/jcm9020296. Retrieved from
  12. Lowe, D. A., Wu, N., Rohdin-Bibby, L., Moore, A. H., Kelly, N., Liu, Y. E., et al. (2020). Effects of time-restricted eating on weight loss and other metabolic parameters in women and men with overweight and obesity: the TREAT randomized clinical trial. JAMA Internal Medicine, 180(11), 1491–1499. doi: 10.1001/jamainternmed.2020.4153. Retrieved from
  13. Magkos, F., Tetens, I., Bügel, S. G., Felby, C., Schacht, S. R., Hill, J. O., et al. (2020). A perspective on the transition to plant-based diets: a diet change may attenuate climate change, but can it also attenuate obesity and chronic disease risk?. Advances in Nutrition (Bethesda, Md.), 11(1), 1–9. doi: 10.1093/advances/nmz090. Retrieved from
  14. Mancini, J. G., Filion, K. B., Atallah, R., & Eisenberg, M. J. (2016). Systematic review of the mediterranean diet for long-term weight loss. The American Journal of Medicine, 129(4), 407–415. doi: 10.1016/j.amjmed.2015.11.028. Retrieved from
  15. Manheimer, E. W., van Zuuren, E. J., Fedorowicz, Z., & Pijl, H. (2015). Paleolithic nutrition for metabolic syndrome: systematic review and meta-analysis. The American Journal of Clinical Nutrition, 102(4), 922–932. doi: 10.3945/ajcn.115.113613. Retrieved from
  16. Masood W, Annamaraju P, Uppaluri KR. (2020). Ketogenic diet. In: StatPearls [Internet]. Retrieved from
  17. Mazzocchi, A., Leone, L., Agostoni, C., & Pali-Schöll, I. (2019). The secrets of the Mediterranean diet: does [only] olive oil matter?. Nutrients, 11(12), 2941. doi: 10.3390/nu11122941. Retrieved from
  18. MedlinePlus. (2020, Jul). Meditteranean diet. Retrieved on Jul 14, 2021 from
  19. National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK). (2017, Jul). Choosing a safe and successful weight loss program. Retrieved July 14, 2021 from
  20. Pinto, A. M., Fava, J. L., Hoffmann, D. A., & Wing, R. R. (2013). Combining behavioral weight loss treatment and a commercial program: a randomized clinical trial. Obesity (Silver Spring, Md.), 21(4), 673–680. doi: 10.1002/oby.20044. Retrieved from
  21. Rishor-Olney CR, Hinson MR. (2021) Mediterranean diet. In: StatPearls [Internet]. Retrieved from
  22. Rynders, C. A., Thomas, E. A., Zaman, A., Pan, Z., Catenacci, V. A., & Melanson, E. L. (2019). Effectiveness of intermittent fasting and time-restricted feeding compared to continuous energy restriction for weight loss. Nutrients, 11(10), 2442. doi: 10.3390/nu11102442. Retrieved from
  23. Trepanowski, J. F., Kroeger, C. M., Barnosky, A., Klempel, M. C., Bhutani, S., Hoddy, et al. (2017). Effect of alternate-day fasting on weight loss, weight maintenance, and cardioprotection among metabolically healthy obese adults. JAMA Internal Medicine, 177(7), 930. doi: 10.1001/jamainternmed.2017.0936. Retrieved from
  24. Tyson, C.C., Nwankwo, C., Lin, PH. et al. The dietary approaches to stop hypertension (DASH) eating pattern in special populations. Current Hypertension Report 14, 388–396 (2012). doi: 10.1007/s11906-012-0296-1. Retrieved from
  25. U.S. Food and Drug Administration (FDA). (2021). Sodium in your diet. Retrieved on July 14, 2021 from